1. Field of the Invention
The present invention relates to a method of fabricating an element including nanogap electrodes.
2. Description of Related Art
Lately, devices have become smaller and more highly dense, and there is a demand for a finer electric element. As one example, there is a known element where voltage is applied between two elements with a fine gap (nanogap) therebetween to enable switching operation.
Specifically, for example, an element is developed including silicon oxide and gold which are stable material and the element is fabricated by a simple fabricating method called shadow evaporation. The element can be repeatedly used stably in switching operation (for example, Japanese Patent Application Laid-Open Publication No. 2005-79335).
Also, for example, an element which can be integrated at a higher density and which is more easier to integrate is developed, and the element includes two electrodes aligned vertically with a nanogap therebetween (for example, Japanese Patent Application Laid-Open Publication No. 2008-243986). Specifically, the element described above is fabricated by the following steps for example, (a) forming a lower electrode (first electrode) on an upper surface of an insulating substrate, (b) forming an insulating film so as to cover the first electrode, (c) forming a depressed section (depressed section on hole) on the insulating film to expose a portion of the upper surface of the first electrode (d) forming an upper electrode (second electrode) in the opening section and inside the depressed section on the upper surface of the insulating film by shadow evaporation and with this, nanogap electrodes are formed.
However, in the element described in Japanese Patent Application Laid-Open Publication No. 2008-243986, the depressed section is fabricated by forming a resist pattern on an insulating film using a device to expose light, etc., and then etching only portions on the insulating film where the resist pattern is not formed. Due to the influence of variation of light exposure and variation of etching, variation of shape of the depressed section occurs. Also, in the element described in Japanese Patent Application Laid-Open Publication No. 2008-243986, the electrodes are fabricated by shadow evaporation and due to the influence of variation of shadowing angle in shadow evaporation, variation of the shapes of the electrodes occurs. Therefore, there is a problem that it is difficult to perform mass production of elements including nanogap electrodes with a certain distance therebetween due to the influence of variation in fabrication.